"I don't know what that was,'' said Isner, the only seeded American male in the singles draw, at No. 13. "Maybe he was trying to get some crowd support.''

Struff did not succeed. Even if he had gotten the Louis Armstrong Stadium spectators on his side, the 77th-ranked Struff still had to deal with Isner's serve, which hits 138 mph, and pounded out 30 aces.

Once Isner got through the first-set tiebreaker in his 7-6 (5), 6-4, 6-2 victory, Struff was cornered, putting only 39 percent of Isner's serves in play, without a single return winner. He got to break point only once, and couldn't convert that.

That result, coupled with Querrey's 6-3, 6-4, 6-4 cruise past No. 28 seed Guillermo Garcia-Lopez of Spain -- Querrey had 16 aces and saved the only two break points Garcia-Lopez saw -- led directly to more talk about the middling state of U.S. men's tennis.

Besides Isner and Querrey, only 90th-ranked Tim Smyczek, who plays his second-round match Friday, is alive among Yanks in the Open.

Querrey, ranked as high as 17th in 2011 but now at No. 57, said he is "feeling much better than my ranking,'' on a seven-match winning streak. And, yes, he finds talk of disappointing U.S. results tiresome.

"I mean, the question is fair enough,'' he said. "At the end of the day, it's an individual sport. I want all Americans to do well, but I want them to do well for them.''

"That's for you guys to ask about, and certainly rightfully so,'' Isner said. "I get asked it quite a lot. I also have said a lot that I just focus on myself. I'm not worried about the whole state of American tennis. I'm just doing the best I can. Simple as that.''

In the meantime, there hardly is a guarantee that Isner and Querrey will go any farther in the Open. Next up for Querrey is No. 1 seed Novak Djokovic, who Thursday hammered Frenchman Paul-Henri Matthieu, ranked 81st, 6-1, 6-3, 6-0.

Isner will play Germany's Philipp Kohlschreiber, the 22nd seed who defeated Isner in the Open's third round the past two years.

"Playing three years in a row in the third round of this event; it's bizarre,'' Isner said. "But I'm looking forward to it.''